Indie Rock is Energetic

Energy is a Spotify track-level feature measured between 0 to 1, with 0 being the lowest energy and 1 the highest. This boxplot shows that energy is widespread over the Indie genre as a whole. A song’s energy cannot tell us whether it belongs under the general “Indie” label. What it does show, however, is a difference in energy between the three playlists. Spotify’s “Indie Rock” playlist contains the songs with the most energy, with a mean energy of 0.8 and a minimum energy of 0.5. On the other hand, “Indie Folk” has the songs with the least energy with a mean energy of 0.4 and a minimum energy of 0.06. Lastly, “Indie Pop” has its songs’ energies spread out the most with a mean of 0.6, a maximum energy of 0.9, and a minimum energy of 0.1. As an indie listener, this difference in energy is not surprising. Indie folk has a calm and mellow feel and usually uses light acoustic instruments, while indie rock can be louder with a faster tempo and more energetic instruments, such as the drumbs and the electric guitar. Indie pop can have both a calm and energetic feel when listening to it, for example the song “j’s lullaby” by Delaney Bailey is very slow and quiet, while the song “I’m In Love With You” by The 1975 is much more upbeat.

Indie Rock Has The Energy, Indie Folk Is For The Feels, Indie Pop Is Undecided

This graph shows a consistent trend in all three sub-genres: as loudness increases, so does energy. Consistent with the last histogram, energy and loudness are widespread over the Indie genre as a whole. What can be observed again is that Spotify’s “Indie Rock” playlist holds the songs with the most energy and loudness, followed by “Indie Pop” and “Indie Folk.” Hence, the energy and loudness features can help us distinguish Indie songs from each other and categorize them into sub-genres.

Indie folk separates itself from the other two sub-genres through the valence feature. Valence is measured from 0.0 to 1.0 and describes the musical positivity of a track. A song with a high valence (purple in this graph) is described as sounding happy, while a track with a low valence (yellow) sounds sad. Compared to rock and pop, most of the indie folk songs have a negative valence. In other words, Indie Folk is a sad sub-genre.

The song “j’s lullaby” by Delaney Bailey is a clear outlier in this graph. It has the least energy and loudness by far compared to not only the other indie pop songs but also compared to the songs in the other two sub-genres. It is indeed a very mellow and calm song. Another atypical song is “Naked as We Came” by Iron & Wine since it is one of the few songs that is low in energy and loudness but has a positive valence. These specific songs are analyzed further in the “Comparing Pitch” tab.

Does Indie Pop Live Up To Its Name?

This graph shows the relationship between a track’s popularity and danceability. Spotify’s danceability audio feature measures how suitable a track is for dancing based on tempo, rhythm, and beat. 0 means not danceable and 1 means very danceable. Track popularity is a measure between 0 and 100, with 100 being most popular and 0 being least popular. Track popularity is measured based on how many times the track has been played. We can observe that there is no clear relation between popularity and danceability; a popular song can be either danceable or not, and vice versa. The purple horizontal line represents the mean track popularity of each playlist, and the blue vertical line represents the mean danceability.

Indie pop, based on its name, should have the songs with the most popularity. It does indeed have the most popular song in the entire playlist, “ceilings” by Lizzy McAlpine, with a popularity of 91. It also, however, has the song with the least popularity, “Scandal” by Emerald. Surprisingly, the “Indie Pop” playlist has the lowest popularity mean of 52. “Indie Folk” has a mean of 57, and “Indie Rock” has the highest mean of 59. Hence, Spotify’s “Indie Pop” playlist does not have the most popular songs in contrast to its name. All three playlists have the majority of their tracks within a popularity measure range of 40 and 80. The three playlists therefore do not differ too much in popularity.

Although indie pop does not win the popularity contest, it does have the highest average danceability score of 0.7. Indie folk and rock have similar averages of 0.5.

We can also observe the different modes, major or minor, used in each track. Both Indie Folk and Pop have the majority of their tracks in a major key, while Indie Rock has about half of its tracks in a minor key.

In summary, track popularity is quite similar across the three playlists, Indie Pop is the most danceable playlist, and Indie Rock has songs played in more minor keys than the other two sub-genres.

Typical Indie Rock: Simple Chroma & Complex Timbre

Typical Indie Folk: Repeating Chroma & Simple Timbre

Iron & Wine is an American indie folk singer-songwriter. His songs have the typical indie folk sound, which is confirmed by the fact that 2 out of the 50 songs in Spotify’s “Indie Folk” playlist are his. Although he is considered an indie artist, he has never been an independent artist. His first album “The Creek Drank the Cradle” was released in 2002 on the Sub Pop label. Hence, “Flightless Bird, American Mouth” by Iron & Wine is an interesting song to analyze as it is labeled an indie song, but was not independently released.

The self-similarity matrices we see on the left are to be expected. Indie folk songs are characterized by a very simple structure known as a strophic form, a particular sequence is repeated over and over in the song. In this particular song, a verse is repeated four times with the same melody, but differing lyrics.

When considering timbre, the only two instruments used during the song are the guitar and tambourine. The timbre-based matrix mostly contains dark blocks, which demonstrates the homogeneity of instrumentation. The thin bright lines simply indicate that one instrument is not being played anymore or another is added. These lines help us discern the four verses through four homogeneous blocks along the diagonal.

The chroma-based self-similarity matrix shows the repeating use of pitch, throughout the song. As described earlier, the dark diagonal lines indicate repetition. Hence, a particular section with varying pitch is repeated over and over again throughout the song.

In summary, an indie folk song is characterized by homogeneous instrumentation and repeating pitch.

Typical Indie Pop: Simple Chroma & Simple Timbre

“Ceilings” by Lizzy McAlpine is the most popular song in the “Indie Pop” playlist. She released self-released her first EP “Indigo” in 2018. She released “Ceilings” in 2022 under the AWAL label. AWAL, or Artists Without A Label, is a British company that serves as an alternative to the traditional music label deal, offering artists and independent labels without them giving up ownership or control. Hence, although “ceilings” was released under a label company, it could still be considered “independent.”

“Ceilings” has the following structure: verse 1, chorus, verse 2, chorus, outro. The first 20 seconds of the song consists of an acoustic guitar solo, and then McAlpine joins in with vocals. We can see a slight change in timbre at that time, marking the beginning of the first verse. The chorus starts at 60 seconds, and we see a thin yellow line in the timbre matrix at this time. This could be due to her change in her use of breath. When she starts singing the chorus, McAlpine sings in a more breathy, airy tone.

At 90 seconds, which marks the beginning of verse 2, half notes played by a base and faint percussion sounds are added to the background of the vocals. This could explain the sudden bright change we can observe in the chroma matrix. A violin than comes in just before 100s, which is what the thin bright line in the timbre matrix could be showing.

At 120 seconds, Lizzy McAlpine sings the second chorus in a higher pitch. This is represented by a bright line in the chroma matrix. Just before 150 seconds, she begins the outro in yet another higher pitch, which is also represented in the chroma matrix.

In summary, the structure of Lizzy McAlpine’s “ceilings” can be clearly seen through analyzing both chroma-based and timbre-based self-similarity matrices.

Indie Keys

This histogram shows the distribution of keys in each indie subgenre playlist. The most common used keys in Indie Pop are C and C#. This is to be expected, as C and G major are the most common key used in pop music. Although G major is one of the most common keys used in pop music, G is surprisingly the least common key in Indie Pop. Hence, indie pop follows the pop-genre norm when it comes to having songs with C as a key, but the minority of the songs are in the key of G. The other two indie genres have a less distinct majority key. Indie Folk has the majority of its songs in the keys C, D, E, and F, and the minority in keys G# and A#. Indie Rock has the majority of its songs in the keys C, D, G, and A, and the minority in keys D#, G#, and A#. C is thus the most common key used in all three genres, followed by D. Overall, the keys used in each subgenre are widespread, with some more and others less common.

“White Winter Hymnal” by Fleet Foxes

A chordogram is a visual representation of the different chords used in a song at any given time. These are made by comparing the chords in the audio recording of the song to a template of predefined chord models. The darker sections in the chordogram are, the more similar those chords are to the template, meaning this chord is being played at a particular time.

“White Winter Hymnal” by Fleet Foxes is another typical indie folk song. It is very repetitive in its melody and lyrics. Its structure consists of an intro followed by the chorus three times. This is very characteristic of indie folk music. The only thing that truly changes throughout the song is the chords used throughout. This chordogram shows that “White Winter Hymnal” uses distinct chords during distinct sections of the song. From 0 to 30s, the song is in an E7 chord, this is the intro of the song. From 30 to 40s, the song goes down to an A7 chord, marking a transition between the intro and the first chorus. From 40 to 60s, the chord goes back to E7 for the chorus. From 60 to 70s, the song goes further down to an F# minor, marking another transition from the first chorus to the second chorus, and so on. This variety in chord usage further demonstrates that indie folk can have an interesting chroma.

“I’m In Love With You” by The 1975

diff chords

“A-Punk” by Vampire Weekend

same chord used throughout

Indie Rock is the Fastest, Folk is more Relaxed

Spotify’s tempo feature measures the average tempo of a track. Most popular songs today have a tempo between 100 and 140bpm. This histogram shows that the Indie genre tempo generally lies between 70 and 200bpm, which is overlaps the popular tempo. The means of all three playlists, which are represented by the purple line in the graph, are close to 120bpm. Indie rock has the fastest tempo with an average of 127bpm, followed by pop with 124bpm, and lastly folk has slowest mean tempo of 116bpm. A tempo between 109-132bpm is described as fast, quick, and bright. This describes the tempo of most of the Indie songs in the corpus.

Indie Folk is a slower form of the genre as its mode is centered at 100bpm; 20% of the songs in this playlist have a tempo of 100bpm. Furthermore, three songs in this playlist have a tempo of 70bpm, while the lowest tempo in the other two playlists is 80bpm. Indie folk having a slower tempo is to be expected as a listener, because indie folk does indeed sound slower-paced.

Indie rock and pop have similar tempo distributions. Both their modes are centered around 120bpm, with 20% of their songs having this tempo. This falls right in the middle of the range of tempo of popular songs today. Overall, however, the tempo of all three sub-genres is spread out in a similar manner.

Indie Songs Stick To Their Chosen Tempo

This graph displays information about the overall temporal features of the three playlists. The duration of a song is represented by a point’s size, and the volume is represented by point transparency. As discussed before, we can observe that indie folk is the quietest sub-genre with many orange points being more transparent compared to points from other sub-genres. The duration of the song vary across each sub-genre in similar ways. Hence, the duration of songs cannot help us distinguish between the three playlists, which can vary between 2mins and 6mins.

This graph plots the average tempo of a song in BPM and the standard deviation of the tempo within the song itself. In this case, the standard deviation is a measure of variation in tempo in a song in BPM. Most of the songs are clustered at a standard deviation below 1, indicating that most indie songs stick to one tempo throughout the entire song. Furthermore, all the songs have a standard deviation below 5BPM, which is a variation in tempo that humans are not able to perceive and could therefore simply be due to errors in audio analysis. This consistent tempo is typical in indie music, and this graph confirms that the indie genre does not play much with tempo variation.

Can Spotify’s Audio Features Group Indie Sub-Genres?

# A tibble: 90 × 2
   track.name               n
   <chr>                <int>
 1 25/8                     1
 2 All Is Well              1
 3 Always Like This         1
 4 Another Story            1
 5 Backwards Directions     1
 6 Bad Dream Baby           1
 7 Bad Radio                1
 8 Big Black Car            1
 9 Blue Spirits             1
10 Burning Up Slow          1
# … with 80 more rows

This graph corresponds to hierarchical clustering, which relies on unsupervised machine learning whereby unlabeled songs are grouped together based on their similarity in Spotify’s audio feature measurements. In this cluster, the track names are written at the bottom of each branch, and the color corresponds to which playlist they belong to. The songs that are most similar to each other would be closer together at the end of the tree. Here we can observe that through Spotify’s audio features, the songs in the “Indie Folk” playlist are clustered together, with most of the songs on top being colored in red. The songs in the “Indie Rock” playlist are also clearly grouped together in blue. This means that Spotify is able to use its audio features to distinguish the two indie sub-genres from each other. In contrast, the “Indie Pop” playlist does not have an obvious cluster. This is consistent with indie pop being spread out in energy and valence which we observed earlier. This could be because indie pop has a less recognizable “sound” to it. Wikipedia describes indie pop as “a music genre and subculture that combines guitar pop with DIY ethic in opposition to the style and tone of mainstream pop music.” This “DIY ethic” could be the factor that distinguishes indie pop songs from each other. Artists could have a different spin to a pop sound, making each indie pop song sound slightly different and vary within Spotify’s audio features.

How accurate is the grouping?

This graph is a classification cross-validation graph. Classification relies on supervised machine learning. In this context, classification predicts which genre songs belong to based on Spotify’s audio features. This prediction is then compared to the actual genre the song belongs to in cross-validation. The area of the boxes in this graph correspond to the number of songs that belong to a certain genre based on both prediction and truth. The graph shows that classification using Spotify’s audio features is mostly accurate. The prediction has the majority of the songs grouped in the correct sub-genre. About a quarter of the indie folk songs were predicted to be indie pop, a quarter of the indie pop songs were predicted to be folk, and another quarter of the pop songs were predicted to be rock songs. This further shows the variation in the indie pop songs. Because indie pop does not have a distinct sound from the other two sub-genres, the algorithm has a harder time predicting the correct sub-genre. In contrast, indie rock songs are predicted with approximately 80% accuracy and are more easily distinguished.

Which features are most important for distinguishing the three sub-genres?

This random forrest uses the cross-validation data discussed previously to give us a ranking of feature importance. It measures how useful each Spotify audio feature was for distinguishing the three indie sub-genres. Here we can see that acousticness was the most helpful feature, followed by timbre component 1 and timbre component 2. Timbre refers to the quality of a musical sound that distinguishes different types of musical instruments, or voices. Timbre component 1 refers to the loudness of a song, but, since we already analyzed loudness previously, we will focus on analyzing timbre component 2, which measures a sound’s brightness. The next page will further discuss how acousticness and brightness differ between the three playlists.

Indie Folk is Acoustic, Indie Rock is the Brightest, Indie Pop Enjoys Variety

This graph plots timbre component 2 against acousticness, with the size of the points correspond to the song’s energy level. A general trend that is observed is as acousticness increases, brightness decreases. With brightness being negatively correlated with acousticness, we can assume that an acoustic guitar is not considered to be bright according to Spotify’s audio features. Indie rock is clearly recognized as being energetic and having a bright timbre sound. This could be because of the electric guitar usually used in indie rock. Another observation we can make is that indie folk is an acoustic sub-genre. This is not surprising at all because most indie folk songs are indeed acoustic. Lastly, consistent with the previous analyses, indie pop has songs with varying amounts of energy, brightness, and acousticness.